I would suggest an 18 mm inside width rim. My favorite in that size is the Velocity Dyad because Velocity rims are round and flat, so they are easy and fast to build; just tighten each nipple the same amount you are really close. The Alex DM18 is pretty good, and less expensive. The Sun CR18 is even less expensive, and takes a bit longer to build, and it is not possible to get even tension and a true rim.

I recommend following: https://www.sheldonbrown.com/wheelbuild.html for building wheels.